1. Field of the Invention
The present invention relates generally to a method and a device for treating a wastewater containing nitrogenous compound and more particularly, to a method and a device for treating a wastewater containing both tetramethylammonium hydroxide (TMAH) and ammonium nitrogen by biological treatment.
2. Description of the Related Art
Semiconductor or electro-optical industry usually produces a lot of industrial wastewater containing high concentration ammonium nitrogen and organic nitrogen, such as a strong alkaline TMAH which is often used as a developer liquid. Thus, there is a need to provide a method that can effectively remove the nitrogenous compound contained in the wastewater.
In conventional activated sludge process, a higher hydraulic retention time (HRT) and a higher dissolved oxygen (DO) content are required for degradation of TMAH. Therefore, the treating efficiency is low and the energy consumption is high.
When the nitration-denitration reaction is further proceeded in the activated sludge tank, the ammonium nitrogen and non-degraded TMAH may exist simultaneously in the reaction system. Under such circumstances, the activity of the anammox bacteria can be greatly inhibited by TMAH, resulting in the decrease of the denitration (denitrification) efficiency of the anammox bacteria.
In light of the above, the conventional biological method for treating the wastewater containing both TMAH and ammonium nitrogen has to be divided into at least two individual steps. TMAH degradation is the first step to degrade TMAH into ammonium nitrogen, and denitrification is the second step to degrade the ammonium nitrogen into nitrogen gas. Therefore, more than two reactors are required to proceed with the above-mentioned steps respectively, undesirably increasing the system fabrication cost and enhancing the complexity of operation and maintenance.